Austrosignum latum, Just & Wilson, 2021

Just, Jean & Wilson, George D. F., 2021, Redescriptions and new species in the ‘ Austrosignum-Munnogonium’ complex sensu Just & Wilson (2007), mainly from the Southern Hemisphere (Crustacea Isopoda: Paramunnidae), Zootaxa 4952 (3), pp. 401-447 : 405-408

Austrosignum latum sp. nov.

( Figs 2–3 )

Type fixation. Holotype, T ♂, AM P72158.—Here designated.

Etymology. The Latin adjective latum means broad, alluding to the wide body of the species.

Type Locality. Off La Jolla, California, U.S.A.

Material examined. Holotype. T ♂, 2.0 mm. La Jolla, California, off Scripps Institute of Oceanography , 32°52.09’N, 117°15.69’W, 20 m [65 ft], coll. E. Vetter, on SCUBA, 7 December 1990, stn 65–E, AM P72158.

Paratypes. Same data as holotype, (1 ♀ with embryos, 1.94 mm, 2 juvenile ♀), AM 76851 .

Description. Body ovate, width 0.63 length in female, 0.62 length in male, widest in female at pereionite 3, in male at pereionite 2. Head slightly longer in male than female, length 0.39 width in male, 0.38 in female; length posterior to eyestalks 1.5 anterior length in female, 2.0 in male. Frontal margin shallow convex, with angular lateral margins adjacent to antennae. Eyestalks length 4.0 width, apex rounded, long axis angling forward at approximately 20° in female, 30° in male.

Pereionites 1–7 lateral margins rounded; coxae not visible in dorsal view on 1–4, coxae visible on 5–7, rounded with single simple seta. Pereionite 1 of terminal male greatly enlarged; sagittal length in male 2.2 pereionite midline length, in female 2.0.

Pleon length 1.8 width in female, 1.7 in male. Pleonite 1 width 0.8 distance between uropods, length 0.3 width. Pleotelson with moderate inflection between lateral and proximal margins, and short proximal neck; posterior margin of apex pointed; posterior margin s straight, in female forming 75° angle, 80° in male, set apart from lateral margins by slight concavity at level of uropods.

Antennula articles 1–2 combined extending beyond eyestalk apex; article 1 shorter than 2, tubular; articles 4–6 shorter than 3, article 5 longer than 4 and 6.

Antenna article 3 tubular, width 0.37 length, article 5 distinctly longer than article 4; flagellum with 7 articles, proximal article 0.75 length of second article, article 3–7 short, subequal.

Pereiopod I basis anterior margin smooth, length 2.0–2.6 width (♂, ♀); merus posterior margin with one robust seta distally in female, (absent in terminal male illustrated); carpus triangular, distal width 0.97–1.2 posterior margin length (♀, ♂), posterior margin with 2 large robust setae and 1 distal short robust seta (♀) or simple seta (♂), posterior margin with small crenate projection proximal to each of the two large robust setae; propodus narrowing distally to insertion of dactylus, with crenate ridge on opposing margin.

Male pleopods I covering distal 3–4 length of pleotelson ventral surface; lateral lobes distinctly projecting from lateral margin, width 0.4 distance to midline, distal sublobe with tuft of simple setae; distal projection length 0.32 pleopod total length, forming acute angle, with pointed apices. Female operculum ovoid, width 0.70 length, distal margins slightly concave, apex rounded.

Uropods inserted on lateral margin of pleotelson; protopod absent.

Size. Largest male 2.0 mm. Largest female 1.9 mm.

Distribution. La Jolla Canyon, Southern California, 20 m.

Remarks. For comparison with other species in Austrosignum see Remarks under A. pilosum sp. nov. above.

Figures

FIGURE 2. Austrosignum latum sp. nov. H, holotype, T♂; F, paratype ♀. a, antenna; au, antennula; cvv, head ventral view; up, uropod. Scale for habitus (both specimens), 0.5 mm.

FIGURE 3. Austrosignum latum sp. nov. H, holotype, T♂; F, paratype ♀. op, operculum; p1, pereiopod I; plt vv, pleotelson ventral view.